Some mobile stations provided in moving objects, for instance in telematics, are required to run and remain in a wireless signal waiting process even while main power of the moving bodies is off. Here, the telematics provides various services by the comprehensive utilization of global positioning system (GPS), the Internet, the mobile station and others. For instance, when an automobile or a ship is stolen, a server station determines the location of the stolen automobile or ship through a procedure of sending a command to the stolen automobile or ship that should obtain its own location information by using the GPS to return it to the server station.
When it is difficult for a car owner to find out his own car in premises such as a large parking lot, the owner can easily know the car location through a procedure of calling the server station and having the server station send to the car a command that the car should honk a horn or blink a headlight on and off.
When an airbag is expanded in a car, a telematics station in the car that has detected the expansion automatically sends out its location information along with the information regarding the airbag expansion to the server station. The service station contacts the driver in the car, following which the server station informs the police or an insurance company if emergency such as a traffic accident occurs. Thus, a prompt action can be possible to a trouble such as the accident.
The other services such as remote door lock/unlock, car stereo and hands-free phone cooperative system, and e-mail service have been proposed.
In order to realize the above telematics services, even if the main power of the moving object is off, the mobile station in the moving object must continue to run and remain in a wireless signal waiting process to be ready for receiving a command by a remote access, obtaining present location information, and transmitting a message.
The telematics station, in general, has a CPU for the wireless signal waiting process or the receiving process. In the case, it is conceivable that the CPU intermittently executes the wireless signal waiting process to save power consumption. The above CPU is reset, typically for securing reliable operation, at timing when main power turns on. If the CPU is reset when the CPU is executing the wireless signal waiting process or the receiving process, the process must be interrupted.
Moreover, for instance in the automobile, when an engine starts along with the main power turning on, battery voltage rapidly fluctuates and the reset may not be always successful. Furthermore, quick repeating of the main power ON/OFF may result in failure of reset procedure. FIG. 6 shows relation between wireless power voltage in a telematics station and a reset signal (S-rst) in a case that main power ON occurs shortly after main power OFF. Here, the reset signal is generated by detecting power ON. When a period from OFF to ON of the main power becomes too short, the voltage just before ON insufficiently reduces. Accordingly, the main power ON is not properly detected to result in failure of generating the reset signal.